I am trying to install/configure and run sshguard on debian, I want to check if brute force attacks happen on my server.

I have installed it via apt-get, then I installed systemd and followed the following instructions for configuring https://wiki.archlinux.org/index.php/Sshguard (but those are for archlinux). when I type systemctl enable sshguard
it does not work and I get Failed to issue method call: Unit name sshguard is not valid.

I know this should be a routine task, but it is the first time I have to work with daemon. This stuff is very new to me and I am lost in the documentation. I would like to configure the thing in a way that it default: it bans temporarily ip after 4 failed attempts and of course I would like to start the service at boot.

Maybe I can entirely forget about it because I intend to allow passwordless login (via public key exchange)